As industry has grown rapidly, technology development for environment-friendly clean energy is very urgent for efficient use of energy source and substitution of depleted fossil fuels and environmental preservation.
Accordingly technology development of hydrogen energy gets attention, technology acquisition for hydrogen energy use including hydrogen manufacturing, storage, and transport will be important element to determine national competitiveness and energy security in 21st century.
In case hydrogen is used as energy source, it can be manufactured with water which is infinite and it can be recycled to water after use. And also combustion doesn't emits any pollutant except for only very small amount of NOx.
Besides, hydrogen can be transported as gas or liquid, and can be stored as various type of form such as high-pressure gas, liquid hydrogen, and metal hydride, and etc. And it has merit of being easy to use as fuel by direct combustion or fuel by fuel cell.
Thus, hydrogen can be used in most areas used in from industrial basic materials to normal fuel vehicles, hydrogen planes, and fuel cell, so it is regarded to be the most appropriate for future energy system.
Hydrogen storage technology in hydrogen energy system (production, storage, transport, and use) is most important technology to build up efficient energy system as key technology connecting hydrogen manufacturing and technology using hydrogen.
But, current hydrogen storage technology doesn't meet the target amount presented by US DOE (U.S. Department of Energy).
The technical objectives were revised largely for hydrogen storage capacity for automobile by US DOE in 2009, and target value was 5.5 wt % (room temperature, 100 bar).
Thus, the research is being done for hydrogen storage media focusing on carbon materials among them.
Carbon material is light-weight, and good in corrosion resistance and abrasion resistance, and easy to be treated with.
And also it endures extremely high-temperature, high-pressure conditions compared to other metals, ceramics, and other materials, and it shows 100% reversible hydrogen release behavior by being used as hydrogen storage medium.
Thus, new hydrogen reservoir has been sought continuously, and especially research using carbon material has been proceeded variously.
But, research for lately graphite as highly efficient hydrogen storage medium was recently begun. Graphite, one of abundant natural materials, is of layered space structure where each layer is connected by weak van der Waals force.
For graphite crystal characterized by anisotropic layer structure, carbon atoms in a graphite layer plane are tightly coupled by covalent binding. But layer surface is affected only by weak van der Waals force, thus it is difficult to see the reaction with carbon inside layer surface. Oxidant with strong electron affinity attacks n-electron exposed in graphite layer and easily enters in interlayer and broadens layer spacing without destroying two-dimensional network lattice, and various atom, molecule and ion can be inserted into interlayer, thus it can easily form unique layered compound of graphite.
Accordingly, the inventors of the present invention made efforts to find the optimal functionalization conditions to develop innovative hydrogen storage materials based on conventional graphite powder, and manufactured graphite powder composite containing transition metal particles which is lightweight and affinity of hydrogen is much expressed by manufacturing oxidized graphite powder and introducing transition metal particles of which concentration and diameter are controlled.
Besides, it is confirmed hydrogen storage capacity was improved significantly in the manufactured graphite powder composite containing transition metal particles and the present invention was completed.